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Variable Stars of Globular Clusters in the Large Magellanic Cloud

Variable Stars of Globular Clusters in the Large Magellanic Cloud. Evan McClellan (FSU) Horace Smith (advisor) (MSU) Charles Kuehn (MSU) August 6 th , 2008. Outline. Background- RR Lyrae Variables The Hertzsprung-Russell diagram Globular Clusters Satellite Galaxies Galaxy Formation

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Variable Stars of Globular Clusters in the Large Magellanic Cloud

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  1. Variable Stars of Globular Clusters in the Large Magellanic Cloud Evan McClellan (FSU) Horace Smith (advisor) (MSU) Charles Kuehn (MSU) August 6th, 2008

  2. Outline • Background- • RR Lyrae Variables • The Hertzsprung-Russell diagram • Globular Clusters • Satellite Galaxies • Galaxy Formation • Oosterhoff Dichotomy • NGC2210- • Instruments • Procedure • Results

  3. RR Lyrae Variables • Low mass ~0.8 solar masses • Population II - ~10Gyr old • Radial Pulsation • RRab example: Fundamental Mode

  4. RRc • First Overtone:

  5. The Hertzsprung-Russell Diagram • Temperature vs. Luminosity

  6. Globular Clusters • Globular Cluster H-R Diagram Soar image of NGC2210 (Smith 1995)

  7. Satellite Galaxies • Large and Small Magellanic Clouds, other dwarf spheroidal galaxies • Role in formation of Galactic Halo? NASA/ESA 2008

  8. Oosterhoff Dichotomy • Bimodal Period Distribution for Galactic GCs • OoI: average ‘ab’ P~0.55 days • OoII: average ‘ab’ P~0.65 days • Oosterhoff Gap: 0.58 < P < 0.62 • What about globular clusters in satellite galaxies? Catelan 2005

  9. SOAR- 4.1m mirror Feb. 5-18, 2008 SMARTS- 1.3m mirror Sep. 4-Dec. 31, 2006 NGC2210-Instruments MSU 2005 SMARTS Consortium 2008

  10. For each set of data- Define “star” Find stars Align images Combine Make CMD Putting it all together- Synch star names Calibrate brightness Find “variables” Filter out non-RR-Lyrae Combine lightcurves Plot period vs. amplitude Procedure

  11. Lightcurves • Type “ab” lightcurve

  12. Lightcurves • Type “c” lightcurve

  13. Results • Soar Color-Magnitude Diagram

  14. Results • Smarts Color-Magnitude Diagram

  15. Results • Average ‘ab’ Period=0.596 days

  16. References • Carrol and Ostlie, An Introduction to Modern Astrophysics, Addison-Wesley, 2007 • Catelan, M. 2005, astro-ph/0507464 • Catelan, M. 2006, astro-ph/0604035 • De Lee, N. Variable Stars in NGC6304, MSU 2004 • MSU, 2005, http://www.pa.msu.edu/soarmsu/ • NASA/ESA, 2008, http://www.spacetelescope.org/ • SMARTS Consortium Website, 2008, http://www.astro.yale.edu/smarts/ • Smith, H.A. RR Lyrae Stars, Cambridge University Press, 1995

  17. Thanks • Special thanks to Dr. Horace Smith and Charles Kuehn

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